High production molding machines are an important factor in many industries. The food processing industry is an example. Molding machines are finding increasing utilization in making a wide variety of food products. These molding machines are potentially capable of producing a great increase in product production, over what can be accomplished by manual means, but have had a limited use and utility due to a number of unsolved deficiencies.
Prior art food injection molding machines have been extremely expensive at first purchase, and have had a high maintenance requirement. One source of maintenance problems is the use in some machines of electronic control. The usual electronic maintenance costs are accentuated by the environment in which the food processing machines are utilized. This environment is normally a humid one with high exposure to foreign matter. Further, food processing plants are subject to power surges and other variations in electrical power, that may damage electronic control systems, or cause them to malfunction.
A furher limitation of prior art food molding machines has been, that their production rate is limited by the manner in which the various processing steps are controlled. A timing type of control that allows an adequate time for the previous actuation function to be completed, before initiating the successive actuating function, is undesirable. Such a control inherently must provide for the maximum time that a cycle may take, in order to avoid premature actuation of the successive steps. Additionally, the timing control systems are undesirable because they require excessive set up time and adjustment and because they are susceptible to jamming or other malfunctions when a processing step exceeds the normal maximum time allotment.
Prior art injection molding machines used in processing food on a stick have been unable to insert the stick into the molded product after the food has been completely injected into the mold. This is due to the type of time-sequenced control used in these previous machines. There is a definite improvement in the product, especially in its appearance when the stick is inserted after the food or meat product is injected into the mold cavity (not during its injection), and when mold is completely full. This is because there is no tendency for the stick to be cocked off to one side of the mold by the turbulent inrushing food or meat as it is being forced at high velocities into the mold by the injector piston. This has been the case of previously designed, time-sequenced machines covered by other patents where the stick is driven from one end of the mold at approximately the same time as food or meat is being injected into the other end of the mold. Experimentation shows and has proved that there is a major advantage to driving the stick into the filled mold when the mold "filling" or food product is in a quiescent condition.
Thus it is desirable to have a control system for molding machines that reduces the cycle time, and therefore increases the production rate, especially if such a system is of relatively low initial cost, has a high operational reliability, a low maintenance requirement, and puts the stick in after the mold is full. Such a control system is additionally desirable if it is sensitive to actual malfunctions, to avoid compounding a single malfunction by recycling the machine, when a product has not been perfectly produced and dispensed.